Commercial aviation regulatory agencies have developed required navigation performance (RNP) protocols to facilitate the management of air traffic. Required navigation performance equipped aircraft can safely operate along various routes with less separation than previously needed. This can be significant because less separation means that the number of aircraft that can safely use a particular airspace may increase, and therefore accommodate the increasing demand for air traffic capacity. Under these protocols, RNP values may be assigned to various segments, or legs, of an aircraft's flight plan. For example, during approach an aircraft is typically assigned an RNP value of 0.3 nautical miles (nm). Moreover, for enroute portions of a flight aircraft are typically assigned an RNP value of 2.0 nm, for terminal portions the assigned RNP value is typically 1.0 nm, and when flying over the ocean the RNP value is typically 4.0 or 10.0 nm.
The RNP value defines an airspace within which the aircraft should remain for a predetermined percentage (e.g., 95 percent) of the total flying time. This airspace may be referred to as the RNP Obstacle Evaluation Area or, more simply, the RNP corridor. If the aircraft is RNP capable and if the pilot is appropriately certified, the pilot may attempt to travel the assigned landing leg while remaining within the RNP corridor. If, during the landing attempt, the aircraft breaches an RNP boundary and the leaves the corridor, a warning indicator (e.g., a hazard light) is produced inside the aircraft's cabin and the landing may be aborted and attempted again at a later time.
Closely related to RNP, are what are known as the vertical path performance limits (VPPL), the estimated position uncertainty (EPU), and the vertical estimated position uncertainty (VEPU). The VPPL is defined as a 99.7% limit for system vertical error. The EPU and VEPU are basically the value of the horizontal accuracy and the vertical accuracy, respectively, of the aircraft navigation system. The EPU may be defined as the probability that actual aircraft horizontal position differs from sensed aircraft horizontal position is less than a predetermined value (e.g., 0.05). The VEPU may be defined as a vertical position limit, such that the probability that the aircraft altitude differs from sensed aircraft altitude is less than a predetermined value (e.g., 0.05). It is noted that when the EPU and VEPU are reported by a global positioning system (GPS) or a global navigation satellite system (GNSS), the EPU is sometimes referred to as the Horizontal Figure of Merit (HFOM) and the VEPU is sometimes referred to as the Vertical Figure of Merit (VFOM).
Many conventional aircraft display systems include various means for displaying current RNP, as well as EPU and VEPU values to a flight crew. These display systems include implementations for displaying the current RNP, EPU, and VEPU values both numerically and non-numerically. However, the RNP, EPU, and VEPU values may not be displayed to the flight crew in a highly intuitive manner. Moreover, the EPU and VEPU values for other traffic entities within range of the aircraft may not be displayed at all.
Hence, it would be desirable to provide a one or more displays for rendering aircraft RNP, EPU, and VEPU values non-numerically and in a fairly intuitive manner and/or the EPU and VEPU values for other traffic entities within range of the aircraft. The present invention addresses at least this need.